Synthesis and advanced dehydrogenation properties of niobium-based ammine borohydride

In this paper, niobium-based ammine borohydride has been synthesized via a simple ball milling of NbCl5.5NH(3) and MBH4 (M = Li, Na) with a molar ratio of 1:5. Thermogravimetric analysis-mass spectrometry (TGA-MS) and temperature-programmed-desorption (TPD) results revealed that the dehydrogenation of NbCl5.5NH(3)/5LiBH(4) and NbCl5.5NH(3)/5NaBH(4) mixtures showed a two-step decomposition process with a total of 8.1 wt.% and 11.2 wt.% pure hydrogen evolution upon heating to 250 degrees C, respectively. Isothermal TPD results showed that over 6 wt.% and 10.4 wt.% pure hydrogen were liberated from NbCl5.5NH(3)/5NaBH(4) within 60 min at 150 degrees C and 220 degrees C, respectively. Fourier transform infrared spectroscopy (FTIR) and isotope tagging measurements demonstrated that the dehydrogenation mechanism of niobium-based ammine borohydride is not only based on the combination reaction of BH and NH groups, but the BH center dot center dot center dot HB and NH center dot center dot center dot HN homo-polar interactions also contribute to the H-2 formation. Copyright (C) 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.